The present invention relates generally to the manufacturer of elastomeric products, and more particularly articles of manufacturer wherein a yarn or roving is preimpregnated with an elastomeric matrix for subsequent, delayed, filament winding or making into laminates and to the processes for making such compositions. The product is what is known in the art as an "elastomeric prepreg."
Various elastomerics have been used as major or minor constituents of coating compositions, frequently blended with other materials which effect the properties of the coatings. However, up until now, the manufacturer of these elastomeric systems have been performed in situ, involving wet winding. Elastomers include natural rubber or synthetic elastomeric polymers. Wet winding requires dissolving the rubber elastomer in a mixture of solvents. Control of the solvents required to put many of the elastomers e.g. VAMAC rubber, which is a trademark for a elastomeric polymer manufactured by DuPont, into solution requires the use of extensive environmental control equipment. This equipment is not available at most filament winders. Manufacturers of typical nonelastomeric composites involving such well-known rovings as fiberglass, Kevlar, and graphite when combined with their resin systems do not usually require such environmental control equipment because there are no toxics or carcinogens driven off during the process. However, for manufacturing convenience, epoxy, phenolic, polyesters, and some other systems are currently available in prepreg form. In all of these prepregs the cure of the resins is started but not completed and are known as B-stage materials.
While all of these prior art products are somewhat related they are all distinguishable over the present invention in that they are either non-elastomerics or if they involve elastomerics they are cured, in situ. Tire manufacturing is a typical process involving elastomeric composites which are totally cured. Pressure-sensitive adhesives are examples of elastomerics which are at least partially cured.
The object of this invention is to provide a prepreg wherein the yarn or roving is impregnated with an elastomeric matrix which is wound on spools or rolls for later use in filament winding or making into laminates.
It is a further object of this invention to provide a rubber matrix impregnated yarn or roving, unlimited in types, wound on spools or rolls for subsequent filament winding or making into laminates without the use of special environmental control equipment to control the solvents required to put the rubber matrix in solution.
Still another object of the present invention is to provide a yarn or roving preimpregnated with an elastomeric matrix system which is left in the uncured state as opposed to a partially cured state by the removal of the solvents required in order to coat the yarn or roving with an elastomeric matrix.
Another object of the present invention is to provide an elastomeric prepreg for winding on the outside skin of a missile so as to provide an integral over wrap shield or by applying layers with impregnated cloth material to the outer surfaces of a graphite composite structure. These outer layers provide damage resistance and insulation required for specified solid propellant motor cases, all to be finally cured by the application of heat and pressure.